Structure of the spin-glass state of La2-xSrxCuO4:: The spiral theory

Starting from the t-J model, we derive the effective field theory describing the spin dynamics in insulating La2-xSrxCuO4, x less than or similar to 0.055, at low temperature. The theory results in a disordered spiral ground state, in which the staggered component of the copper spins is confined in a plane determined by the spin anisotropies. The static spin structure factor obtained in our calculations is in perfect agreement with neutron scattering data over the whole range of doping in both, the Neel and the spin-glass phase. We show that topological defects (spin vortex-antivortex pairs) are an intrinsic property of the disordered spiral ground state.